1. Technical Field
The present invention is directed toward a check rail lock for use with a double-hung window, and more particularly toward a check rail lock including a handle and cam which are lockable in both the open and closed positions.
2. Background Art
A check rail lock draws together meeting rails of an upper and lower sash of a double-hung window and locks the sashes against opening movement. The check rail lock has a housing which mounts a rotatable cam for movement between locked and unlocked positions and which engages a keeper in a locked position The cam is limited to movement between the locked and unlocked positions.
Some prior art cam locks have included a spring washer rotatable with a cam and a coacting detent structure on the spring washer and the housing which releasably retains the cam in either locked or unlocked positions. However, it is possible to cause such check rail locks to open by operating the handle with a stiff wire from outside the window. Thus, an intruder can gain access through the double-hung window.
Still other cam locks have provided a mechanism for locking the handle and cam in the locked position in order to keep an intruder from opening the lock from the outside by manipulating the lock with a wire or other tool inserted between the sashes or through a security grate over the window. However, such prior art locks have been freely movable when not in the locked position, with the result being that the lock when opened can be inadvertently moved toward the closed position with the cam extending out of the housing. In such a condition, which will typically not be noticed by a person thereafter moving the window, movement of the window can cause the cam to hit the keeper, grill bars or other obstructions and break the check rail lock or window.
The present invention is directed toward overcoming one or more of the problems set forth above.